The present application claims priority under 35 U.S.C. xc2xa7119 of German Patent Application No. 197 53 819.3, filed on Dec. 4, 1997, the disclosure of which is expressly incorporated by reference herein in its entirety.
1. Field of the Invention
The present invention relates to a tread profile of a snow tire.
2. Discussion of Background Information
Various and conflicting demands are placed on snow tires. That is, a snow tire is supposed to ensure good traction on snow and ice and good handling characteristics, e.g., as in summer tires. However, these demands require conflicting measures in the design of the snow tire, i.e., to provide either a snow tire with either good winter characteristics, e.g., good traction on ice and snow and comparatively poor handling on dry roads, or a summer tire with good handling on dry roads, but comparatively poor winter characteristics.
The present invention provides a tread profile for a snow tire with both good winter characteristics, e.g., good traction on ice and snow, and good handling on dry roads.
The present invention contemplates a tread profile that includes a plurality of profile block rows aligned in a circumferential direction and spaced in an axial direction from a first tire shoulder, adapted to be positioned toward an outside of the vehicle in an operating state of the tire, to a second tire shoulder, adapted to be positioned toward an inside of the vehicle in an operating state of the tire, and a plurality of channels aligned in the circumferential direction and arranged to axially separate the plurality of profile block rows from each other. The plurality of channels includes a first circumferential channel positioned to divide the tread profile into two axial regions of functionally different structure. Each axial region axially extends from an associated tire shoulder to the first circumferential channel. The profile block elements in the axial region extending from the first circumferential channel to a first tire shoulder directed away from the vehicle during an operating state of the tire are constructed with a higher lateral thrust stiffness than the profile block elements in the axial region extending from the first circumferential channel to a second tire shoulder pointing toward the inside of the vehicle in the operating state of the tire on the vehicle.
As a result of the stiffer construction of the profile block elements on the side of the tread profile pointing toward the outside of the vehicle, the stiffness desired for handling may be substantially ensured on this side of the tire (i.e., the handling side), which is important for handling, and, therefore, good handling on dry roads is provided. In the axial tread region that is less important for handling (i.e., the winter side), the low stiffness of the profile blocks that is important for good traction on snow and ice are provided, and, therefore, good winter traction is substantially ensured.
In the exemplary embodiment of the present invention, it may be preferable to arrange the profile blocks such that the profile blocks in the axial region directed toward the inside of the vehicle have structural factors, both along a circumferential direction and perpendicular to circumferential direction, between approximately 10 and 50% higher than the structural factors of the profile blocks in the axial region directed toward the outside of the vehicle. Thus, an especially high number of traction edges may be created on the winter side. Further, a large number of sipes, which are substantially responsible for the structural factor, may make the profile blocks even softer on the winter side. Conversely, the handling side may be stiffer due to the lower number of the sipes creating the traction edges. The structural factor in the circumferential direction is a sum of the profile block edges and sipes projecting in the circumferential direction, and the structural factor in the direction perpendicular to the circumferential direction is the sum of the profile block edges and sipes projecting perpendicular to the circumferential direction.
The exemplary embodiment may also preferably include a pitch count in the axial region directed toward the inside of the vehicle that may be greater than pitch count in the axial region directed toward the outside of the vehicle. As a result of this construction, more and smaller profile elements may be created on the winter side of the tire than on the handling side of the tire. Thus, even more profile edges may be provided for facilitating winter taction. As a result of this feature, the handling side may also be more stiffly constructed.
Free visibility through a circumferential groove is a measure of ice traction and snow traction. As a result, the tire of the present invention may be formed such that at least one additional circumferential channel or groove may be provided in both axial regions to separate two adjacent profile block rows from one another. It may be preferable to form the at least one additional circumferential channel in the axial region directed toward the vehicle to have an exposed groove cross-section that is smaller than the exposed groove cross-section of the at least one additional circumferential channel in the axial region directed toward the outside of the vehicle. It may be preferable still to provide the exposed groove cross-section of the at least one additional circumferential channel in the axial region directed toward the vehicle with a width that is at least half as large as the exposed groove cross-section of both the first circumferential channel and/or the at least one additional circumferential channel in the axial region directed toward the outside of the vehicle. In this manner, the tire of the present invention may exhibit further improvement over known tires in ice traction characteristics and in braking characteristics on snow without jeopardizing handling characteristics on dry roads.
The profile block elements on the winter side of the tire may include a plurality of sipes that extend through the profile block elements, and it may be preferable to arrange the sipes such that a distance between a peripheral edge of a respective profile block element and an adjacently arranged sipe arranged within the respective profile block element is between approximately 7 and 15% greater than a distance between the substantially parallelly arranged sipes arranged within the respective profile block element. Further, it may be preferable to provide a sipe depth at the edges of the profile block element that is between approximately 10 and 20% smaller than in a region between the edges of the profile block, i.e., in the interior of the profile block element. Thus, the profile block elements may be constructed with a hard, wear-reducing shell outside and a soft core inside that improves winter characteristics.
The exemplary embodiment of the present invention may preferably include at least one profile block row formed by successively arranged profile block elements in the circumferential direction that are separated by diagonally running channels forming transverse edges to define the profile block elements in the circumferential direction, that include longitudinal edges to laterally define the profile block elements, and that include spaced sipes that extend through the profile block element at an angle between approximately 80 and 110xc2x0 to the longer diagonals of a trapezoid formed by the transverse edges and the longitudinal edges. This particular arrangement may make possible a particularly high effective edge length in the profile block elements. Further, the exemplary embodiment may preferably include, at the tire shoulders and in at least one profile block row arranged between the tire shoulders, profile block rows formed by successively arranged profile block elements in the circumferential direction that are separated by diagonally running channels forming transverse edges to define the profile block elements in the circumferential direction, that include longitudinal edges to laterally define the profile block elements, and that include spaced sipes that extend through the profile block element. The sipes within the tire shoulder profile block elements may be oriented substantially parallel to the diagonally running channel defining the profile block elements in the circumferential direction, and the sipes within the profile block elements of the profile block row between the tire shoulders may be oriented to extend through the profile block element at an angle between approximately 80 and 110xc2x0 to main diagonals of a trapezoid formed by the transverse edges and the longitudinal edges. This particular arrangement may make possible a particularly highly effective edge length in the profile block elements of the winter side, and a smaller effective edge length, and, thereby, greater stiffness in the profile block elements of the handling side.
In accordance with the present invention, it may be preferable to further include an additional profile block row in the axial region directed toward the inside of the vehicle that may be separated from a profile block row of the second tire shoulder by a second circumferential channel (groove). These two adjacent profile block rows may be formed with successively arranged profile block elements in a circumferential direction that may be separated by diagonally running cross channels forming transverse edges to define the profile block elements in the circumferential direction, that include longitudinal edges to laterally define the profile block elements, and that may include spaced sipes that extend through the profile block element. The cross channels may extend over both profile block rows and axially inwardly from the second tire shoulder under constant inclination. The cross channels may be arranged to be offset from one another in the circumferential direction at a transition position through the second circumferential channel such that an end of the cross channel of the second tire shoulder block row pointing toward the second circumferential channel occupies a same circumferential position as an end of the cross channel of the adjacent profile block row directed toward the second circumferential channel. This particular arrangement may facilitate a reliable outflow of water through the profile channels and, thereby, substantially ensure good hydroplaning (aquaplaning) characteristics.
The tire of the present invention may also include at least one additional profile block row in the axial region directed toward the inside in the vehicle that may be separated from a profile block row of the second tire shoulder by a second circumferential channel (groove). The profile block elements of the second tire shoulder block row and of the additional profile block row(s) may each include a plurality of transverse sipes having sinusoidal progressions in the longitudinal direction of sipes and that are separated from one another. The progression of the sipes along a depth of the sipe may be formed to be continuously phase-shifted in the longitudinal direction. Thus, a phase shift occurs along the depth of the sipe, which is substantially constant in accordance with a line of inclination having an angle of inclination xcex1 to the radial direction, and adjacent sipes in a same profile block element may be formed to have a substantially opposite phase shift along the depth of the sipe, in accordance with a line of inclination having an angle of inclination xcex2 to the radial direction. In this manner, the two lines of inclination, which are inclined in opposite directions, may subtend an angle xcex3=xcex1+xcex2. Thus, angle xcex3 is a measure for the twist of the sipes of the profile block elements. Twist angle xcex3 in the profile block elements of the second tire shoulder block row may be greater than twist angle xcex3 of the additional profile block row(s). In particular, twist angle xcex3 in the second tire shoulder profile block elements may be between approximately 35 and 60xc2x0 and twist angle xcex3 of the additional profile block row(s) may be between approximately 15 and 25xc2x0. Thus, this particular arrangement may make possible a greater stiffening of the profile block elements in the shoulders as compared to the profile block elements between the shoulders. The stiffening in the shoulders may additionally improve the handling characteristics with the good winter traction characteristics provided by the softer design of the center region of the tire. The stiffer design in the second tire shoulder may make possible the additional incorporation of further sipes in these profile elements, which, simply by providing additional edges, would further improve the winter traction. Moreover, the row of second tire shoulder blocks may be reduced in stiffness, thereby, further improving the winter traction.
The tire of the present invention may include two shoulder profile block rows and at least one additional profile block row positioned between the two shoulder profile block rows. One circumferential channel (groove) at a time may be formed between the profile block rows. The profile block elements of the at least one of the tire shoulder block rows and of the additional profile block row(s) may each include a plurality of transverse sipes having sinusoidal progressions in the longitudinal direction of sipes and that are separated from one another. The progression of the sipes along a depth of the sipe may be formed to be continuously phase-shifted in the longitudinal direction. Thus, a phase shift occurs along the depth of the sipe, which is substantially constant in accordance with a line of inclination having an angle of inclination xcex1 to the radial direction, and adjacent sipes in a same profile block element may be formed to have a substantially opposite phase shift along the depth of the sipe, in accordance with a line of inclination having an angle of inclination xcex2 to the radial direction. In this manner, the two lines of inclination, which are inclined in opposite directions, may subtend an angle xcex3=xcex1+xcex2. Thus, angle xcex3 is a measure for the twist of the sipes of the profile block elements. Twist angle xcex3 in the profile block elements of the at least one tire shoulder block row may be greater than twist angle xcex3 of the additional profile block row(s). In particular, twist angle xcex3 in the at least one tire shoulder profile block elements may be between approximately 35 and 60xc2x0 and twist angle xcex3 of the additional profile block row(s) may be between approximately 15 and 25xc2x0. Thus, the higher twist in the shoulders has the effect that these profile elements are more stiffly constructed than the profile elements in the center region. The stiffening in the shoulders improves the handling characteristics, while the softer design of the center region substantially ensures good winter traction characteristics. Further, the stiffer design in the second tire shoulder makes possible the additional incorporation of further sipes in these profile elements so as to further improve winter traction simply by providing additional edges. Moreover, the row of second tire shoulder blocks may reduce stiffness, thereby, further improving winter traction.
Accordingly, the present invention is directed to a tread profile of a snow tire for a vehicle. The tread profile includes a plurality of profile block rows aligned in a circumferential direction and distributed in an axial direction from a first tire shoulder adapted to be positioned toward an outside of the vehicle in an operational state of the tire on the vehicle to a second tire shoulder adapted to be positioned toward an inside of the vehicle in an operational state of the tire on the vehicle. The tread profile also includes a plurality of channels aligned in a circumferential direction and being arranged to axially separate the plurality of profile block rows from each other, and the plurality of channels includes a first circumferential channel positioned to divide the tread profile into two axial regions of functionally different structure, and each axial region axially extending from one of the first and second tire shoulders to the first circumferential channel. The plurality of profile block rows includes a plurality of profile block elements, and the plurality of profile block elements in the axial region extending from the circumferential channel to the first tire shoulder have a higher lateral thrust stiffness than the plurality of profile block elements in the axial region extending from the first circumferential channel to the second tire shoulder.
In accordance with another feature of the present invention, a structure factor along the circumferential direction and along a direction perpendicular to the circumferential direction in the plurality of profile block elements in the axial region extending from the first circumferential channel to the second tire shoulder is between approximately 10 and 50% higher than a structure factor along the circumferential direction and along the direction perpendicular to the circumferential direction in the plurality of profile block elements in the axial region extending from the first circumferential channel to the first tire shoulder.
In accordance with another feature of the present invention, a pitch count in the axial region extending from the first circumferential channel to the second tire shoulder is greater than a pitch count in the axial region extending from the first circumferential channel to the first tire shoulder.
In accordance with still another feature of the present invention, at least one additional circumferential channel is positioned in the axial region extending from the first circumferential channel to the second tire shoulder and in the axial region extending from the first circumferential channel to the first tire shoulder to separate adjacent profile block rows from each other. An exposed groove cross-section of the at least one additional circumferential channel in the axial region extending from the first circumferential channel to the second tire shoulder is smaller than an exposed groove cross-section of the at least one additional circumferential channel in the axial region extending from the first circumferential channel to the first tire shoulder pointing toward the vehicle outside in the operating state of the tire on the vehicle, and the exposed groove cross-section of the at least one additional circumferential channel in the axial region extending from the first circumferential channel to the second tire shoulder is at least half as large as an exposed groove cross-section of the first circumferential channel and the exposed groove cross-section of the at least one additional circumferential channel in the axial region extending from the circumferential channel to the first tire shoulder.
In accordance with a further feature of the present invention, the plurality of profile block elements in the axial region extending from the first circumferential channel to the second tire shoulder includes a plurality of sipes that are substantially parallelly arranged and that extend over the plurality of profile block elements. A distance between a peripheral edge of a respective profile block element and an adjacently arranged sipe arranged within the respective profile block element is greater than a distance between the substantially parallelly arranged sipes arranged within the respective profile block element. Further, the distance between the peripheral edge of the respective profile block element and the adjacently arranged sipe arranged within the respective profile block element is between approximately 7 and 15% greater than the distance between the substantially parallelly arranged sipes arranged within the respective profile block element.
In accordance with a still further feature of the present invention, the plurality of profile block elements in the axial region extending from the first circumferential channel to the second tire shoulder include a plurality of sipes that are substantially parallelly arranged and extending over the plurality of profile block elements. A depth profile of the sipes of a respective profile block element extending through the respective profile block element may have a smaller depth at edges of the respective profile block element than at an interior of the respective profile block element. Further, the depth of the sipes at the edges of the respective profile block element may be between approximately 10 and 20% less than the depth of the sipe at the interior of the respective profile block element.
In accordance with another feature of the present invention, at least one of the plurality of profile block rows includes profile block elements successively arranged in the circumferential direction and separated cross channels oriented diagonally to the circumferential direction. The diagonally oriented cross channels form diagonally running transverse edges for the profile block elements in the circumferential direction. The profile block elements of the at least one profile block row include longitudinal edges that define the profile block elements in the axial direction. The profile block elements of the at least one profile block row include a plurality of sipes arranged to be spaced from each other and extending across the profile block element, and the sipes may be oriented to extend at an angle between approximately 80 and 110xc2x0 to a longer diagonal edge of the profile block element.
In accordance with yet another feature of the present invention, the profile block rows located at the first and second tire shoulders and at least one profile block row located between the first and second tire shoulders include profile block elements successively arranged in the circumferential direction and separated cross channels oriented diagonally to the circumferential direction. The diagonally oriented cross channels form diagonally running transverse edges for the profile block elements in the circumferential direction. The profile block elements of the at least one profile block row may include longitudinal edges that define the profile block elements in the axial direction. The profile block elements of the at least one profile block row include a plurality of sipes arranged to be spaced from each other and to extend across the profile block element, such that the sipes arranged within the first and second tire shoulder profile block rows may be oriented substantially parallel to the cross channel forming the diagonally running transverse edges of the profile block elements of the shoulder profile block rows, and the sipes arranged within the at least one profile block row located between the first and second tire shoulders may be oriented to extend at an angle between approximately 80 and 110xc2x0 to a longer diagonal edge of the profile block element.
In accordance with still another feature of the present invention, an additional profile block row may be located within the axial region extending from the circumferential channel to the second tire shoulder and adjacent to the profile block row that includes the second tire shoulder, and a second circumferential channel may be arranged to separate the additional profile block row from the second tire shoulder profile block row. The second tire shoulder profile block row and the additional profile block row may include profile block elements successively arranged in the circumferential direction and separated cross channels oriented diagonally to the circumferential direction. The diagonally oriented cross channels may form diagonally running transverse edges for the profile block elements in the circumferential direction, and the diagonally oriented cross channels may extend over both the second tire shoulder profile block row and the additional profile block rows and extend under substantially constant inclination axially inwardly from the second tire shoulder. The cross channels may be arranged to be offset from each other in the circumferential direction at a transition through the second circumferential channel such that an end of the cross channel of the second tire shoulder profile block row is oriented across the second circumferential channel at a same circumferential position as an end of the cross channel of the second tire shoulder block row.
In accordance with a further feature of the present invention, at least one additional profile block row may be located within the axial region extending from the circumferential channel to the second tire shoulder and adjacent to the profile block row that includes the second tire shoulder, and a second circumferential channel may be arranged to separate the additional profile block row from the second tire shoulder profile block row. The profile block elements of the second tire shoulder profile block row and of the at least one additional profile block row may include a plurality of substantially transverse and substantially sinusoidal sipes separated from each other that extend in a longitudinal direction. The substantially sinusoidal sipes may be arranged such that, along a depth in a radial direction, at least one substantially sinusoidal sipe is continuously phase-shifted in the longitudinal direction, the phase-shift occurring along a line of inclination oriented at an angle xcex1, with respect to the radial direction, and at least one adjacent sipe positioned adjacent to the at least one substantially sinusoidal sipes is continuously phase-shifted in a direction opposite the longitudinal direction, the phase-shift occurring along a line of inclination oriented at an angle xcex2, with respect to the radial direction. In this manner, the lines of inclination for adjacent substantially sinusoidal sipes are arranged to form a twist angle xcex3=xcex1+xcex2, which is a measure for twist of the substantially sinusoidal sipes. Further, the twist angle xcex3 of the second tire shoulder profile block elements may be greater than the twist angle xcex3 of the at least one additional profile block elements. Further, the twist angle xcex3 of the second tire shoulder profile block elements may be between approximately 35 and 60xc2x0 and the twist angle xcex3 of the at least one additional profile block elements is between approximately 15 and 25xc2x0.
In accordance with yet another feature of the present invention, the vehicle includes at least two vehicle wheels that are rotatably mountable outside of a longitudinal vehicle axis.
The present invention may also be directed to a tread profile of tire that includes profile block rows including two shoulder profile block rows and at least one additional profile block row arranged between the two shoulder profile block rows, and one circumferential channel positioned between the profile block rows. The profile block rows include profile block elements, and the profile block elements of at least one of the two shoulder block rows and of the at least one additional profile block row include a plurality of substantially transverse and substantially sinusoidal sipes separated from each other that extend in a longitudinal direction. The substantially sinusoidal sipes may be arranged such that, along a depth in a radial direction, at least one substantially sinusoidal sipe is continuously phase-shifted in the longitudinal direction, the phase-shift occurring along a line of inclination oriented at an angle xcex1, with respect to the radial direction, and at least one adjacent sipe positioned adjacent to the at least one substantially sinusoidal sipes is continuously phase-shifted in a direction opposite the longitudinal direction, the phase-shift occurring along a line of inclination oriented at an angle xcex2, with respect to the radial direction. In this manner, the lines of inclination for adjacent substantially sinusoidal sipes may be arranged to form a twist angle xcex3=xcex1+xcex2, which is a measure for twist of the substantially sinusoidal sipes, and the twist angle xcex3 of the at least one tire shoulder profile block elements may be greater than the twist angle xcex3 of the at least one additional profile block elements. Further, the twist angle xcex3 of the at least one tire shoulder profile block elements may be between approximately 35 and 60xc2x0 and the twist angle xcex3 of the at least one additional profile block elements may be between approximately 15 and 25xc2x0.
The present invention may also be directed to a snow tire including a plurality of profile block rows aligned in a circumferential direction composed of a plurality of profile block elements, a first tire shoulder adapted to be positioned toward an outside of the vehicle during an operational state of the tire, and a second tire shoulder adapted to be positioned toward an inside of the vehicle during an operational state of the tire. A circumferential channel may be positioned to form a handling region located between the first tire shoulder and the first circumferential channel and a winter region located between the second tire shoulder and the first circumferential channel. The profile block elements located within the handling region may have a greater stiffness than the profile block elements located within the winter region.
In accordance with another feature of the present invention, a pitch count in the winter region may be greater than a pitch count in the handling region.
In accordance with still another feature of the present invention, at least a second circumferential channel may be positioned in the winter region to separate adjacent profile block rows, at least a third circumferential channel may be positioned in the handling region to axially separate adjacent profile block rows, and an exposed groove cross-section of the second circumferential in the circumferential direction may be arranged to be at least one-half an exposed groove cross-section of the third circumferential channel in the circumferential direction.
In accordance with still another feature of the present invention, the plurality of profile block elements in the winter region may include peripheral edges delimiting each profile block element and a plurality of sipes located within each delimited profile block element. A distance between one of the peripheral edges adjacent to a longitudinal extent of one of the plurality of sipes and the one of the plurality of sipes may be greater than a distance between adjacent ones of the plurality of sipes.
In accordance with yet another feature of the present invention, one of the plurality of profile block rows within the winter region may be positioned adjacent to the profile block row including the second tire shoulder and a second circumferential channel may be arranged to axially separate the one of the plurality of profile block rows from the second tire shoulder profile block row. The profile block elements of the second tire shoulder profile block row and of the at least one additional profile block row may include a plurality of sipes extending in a longitudinal direction. The sipes may be arranged such that, along a depth in a radial direction, at least one sipe is continuously phase-shifted in the longitudinal direction, the phase-shift occurring along a line of inclination oriented at an angle xcex1, with respect to the radial direction, and at least one adjacent sipe positioned adjacent to the at least one sipe is continuously phase-shifted in a direction opposite the longitudinal direction, the phase-shift occurring along a line of inclination oriented at an angle xcex2, with respect to the radial direction. In this manner, the lines of inclination for adjacent sipes may be arranged to form a twist angle xcex3=xcex1+xcex2.